The invention relates to a method for shaping a workpiece or changing the shape of a workpiece such as a flat plate-like workpiece, for example a sheet metal workpiece.
In known reshaping methods of this type, the workpiece is locally stretched by plastic deformation in the upper or outer surface zones which are impinged upon so that the workpiece is arched convexly against the direction of impingement. Such methods use the shot peening method. It has also been suggested, but not published before the priority date of the present application, to use an impacting stamp which has an elongated effective surface and which is periodically driven by impulses effective on a pulse operated impact piston, and which is guided in a directionally stable manner along an impact line on the upper surface of the workpiece. The impact stamping method has the advantage that it attains a directional deformation effect, especially in the production of workpieces having a simple bent configuration. Therefore the impact method is preferred over the shot peening method. If the workpiece to be shaped comprises a non-uniform wall thickness and/or is to be bent at various radii of curvature, the deformation effect of the impact body or bodies in this method must be altered or varied in a complicated manner at the corresponding surface zones of the workpiece. Such a variation may be achieved by altering the motion impulses supplied to the impact body or bodies, or by altering the impact rate or density, or the advance or feed velocity of the tool and/or workpiece, which requires a structurally complicated impact body control, and therefore makes the practical application of said impacting method much more difficult or even impossible.